JP7347493B2 - Vehicle steering device - Google Patents

Description

The present invention relates to a vehicle steering device.

An electric power steering system (EPS), which is one type of vehicle steering system, applies assist force (steering assist force) to the steering system of a vehicle using the rotational force of a motor. In the EPS, the driving force of a motor controlled by electric power supplied from an inverter is applied to a steering shaft or a rack shaft as an assist force by a transmission mechanism including a speed reduction mechanism.

For example, a vehicle steering device has been disclosed that avoids oversteer and understeer when driving on a low μ road and improves the stability of the vehicle (for example, Patent Document 1).

Japanese Patent Application Publication No. 2006-315634

For example, when the frictional resistance of the road surface is significantly reduced due to ice burns, hydroplaning in puddles, etc., the tire slips and the actual self-aligning torque of the tire decreases. On the other hand, when generating the target steering torque, in a configuration in which the actual steering torque is controlled to follow the target steering torque so as not to be affected by the road surface condition, the target steering torque and the actual self-aligning torque of the tires are There is a possibility that the driver will be delayed in noticing that the tires have lost grip due to the separation, which may delay emergency avoidance maneuvers.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a vehicle steering device that can provide feedback to a driver that the grip force of a tire has been lost.

In order to achieve the above object, a vehicle steering device according to one aspect of the present invention is a vehicle steering device that assists and controls a steering system of a vehicle by driving and controlling a motor that assists steering force. The target steering torque generating section generates a target steering torque of the motor, and the target steering torque generating section generates a torque signal corresponding to a steering angle and a vehicle speed, and a predetermined proportional coefficient to a physical quantity generated by tire slip. A target steering torque is generated according to the difference value from the value multiplied by .

According to the above configuration, steering torque is applied in accordance with changes in vehicle behavior caused by tire slip. This allows the driver to understand that the grip force of the tires has been lost.

As a desirable aspect of the vehicle steering device, it is preferable that the target steering torque generation unit generates the target steering torque by multiplying the torque signal by a torque adjustment coefficient value corresponding to the difference value.

Thereby, it is possible to provide feedback to the driver that the tire grip force has been lost with a small amount of calculation.

As a desirable aspect of the vehicle steering device, it is preferable that the target steering torque generation unit decrease the torque adjustment coefficient value as the difference value becomes larger.

Thereby, the larger the deviation between the torque signal according to the steering angle and vehicle speed and the behavior of the vehicle, the larger the correction amount of the torque signal can be.

In a desirable embodiment of the vehicle steering system, the torque adjustment coefficient value is preferably a positive value of 1 or less.

Thereby, the target steering torque can be appropriately set.

As a desirable aspect of the vehicle steering device, it is preferable that the target steering torque generation unit generates the target steering torque by subtracting a torque adjustment subtraction value according to the difference value from the torque signal.

Thereby, it is possible to provide feedback to the driver that the tire grip force has been lost with a small amount of calculation.

As a desirable aspect of the vehicle steering device, it is preferable that the target steering torque generation section increases the torque adjustment subtraction value as the difference value increases.

Thereby, the larger the deviation between the torque signal according to the steering angle and vehicle speed and the behavior of the vehicle, the larger the correction amount of the torque signal can be.

As a desirable aspect of the vehicle steering device, it is preferable that the torque adjustment subtraction value is smaller than the torque signal.

Thereby, the target steering torque can be appropriately set.

In a desirable embodiment of the vehicle steering device, the physical quantity is preferably self-aligning torque.

Thereby, control can be performed using self-aligning torque as a parameter as a physical quantity generated by tire slip.

In a desirable embodiment of the vehicle steering device, the physical quantity is preferably a yaw rate.

Thereby, control can be performed using the yaw rate as a parameter as a physical quantity generated by tire slip.

In a desirable aspect of the vehicle steering device, it is preferable that the physical quantity is a current command value of the motor.

Thereby, control can be performed using the motor current command value as a parameter as a physical quantity generated by tire slip.

According to the present invention, it is possible to provide a vehicle steering device that can provide feedback to a driver that the grip force of a tire has been lost.

FIG. 1 is a diagram showing a general configuration of an electric power steering device. FIG. 2 is a schematic diagram showing the hardware configuration of a control unit that controls the electric power steering device. FIG. 3 is a diagram showing an example of an internal block configuration of a control unit in an electric power steering device. FIG. 4 is a structural diagram showing an example of installing a steering angle sensor. FIG. 5 is a diagram showing an example of an internal block configuration of the control unit according to the first embodiment. FIG. 6 is an explanatory diagram of the steering direction. FIG. 7 is a flowchart showing an example of the operation of the control unit according to the first embodiment. FIG. 8 is a block diagram illustrating a configuration example of the target steering torque generation section of the first embodiment. FIG. 9 is a diagram showing an example of the characteristics of the basic map held by the basic map section. FIG. 10 is a diagram illustrating an example of the characteristics of a damper gain map held by the damper gain map section. FIG. 11 is a diagram showing an example of the characteristics of the hysteresis correction section. FIG. 12 is a block diagram showing an example of the configuration of the low μ road torque correction value calculating section of the first embodiment. FIG. 13 is a diagram showing changes in actual self-aligning torque on a low μ road. FIG. 14 is a diagram showing an example of the characteristics of the torque adjustment coefficient value map held by the torque adjustment coefficient value map section of the first embodiment. FIG. 15 is a diagram showing an example of the effect of the torque adjustment coefficient value output from the low μ road torque correction value calculating section. FIG. 16 is a block diagram showing an example of the configuration of the twist angle control section of the first embodiment. FIG. 17 is a block diagram illustrating a configuration example of the target steering torque generation section of Modification 1 of Embodiment 1. FIG. 18 is a block diagram illustrating a configuration example of the low μ road torque correction value calculating section of Modification 1 of Embodiment 1. FIG. 19 is a diagram illustrating a characteristic example of the torque adjustment subtraction value map held by the torque adjustment subtraction value map section of Modification 1 of Embodiment 1. FIG. 20 is a diagram illustrating an example of an internal block configuration of a control unit according to Modification 2 of Embodiment 1. FIG. 21 is a block diagram illustrating a configuration example of a target steering torque generation section of a second modification of the first embodiment. FIG. 22 is a block diagram illustrating a configuration example of the low μ road torque correction value calculating section of the second modification of the first embodiment. FIG. 23 is a block diagram illustrating a configuration example of the target steering torque generation section of the third modification of the first embodiment. FIG. 24 is a block diagram illustrating a configuration example of the low μ road torque correction value calculating section of the third modification of the first embodiment. FIG. 25 is a diagram illustrating an example of an internal block configuration of a control unit according to the second embodiment. FIG. 26 is a block diagram illustrating a configuration example of the target steering torque generation section of the second embodiment. FIG. 27 is a block diagram showing an example of the configuration of the SAT information correction section. FIG. 28 is an image diagram showing the state of torque generated between the road surface and the steering wheel. FIG. 29 is a diagram showing an example of the characteristics of the steering torque sensitive gain. FIG. 30 is a diagram showing an example of the characteristics of the vehicle speed sensitive gain. FIG. 31 is a diagram showing an example of the characteristics of the steering angle sensitive gain. FIG. 32 is a diagram showing an example of setting the upper limit value and lower limit value of the torque signal in the limiting section. FIG. 33 is a block diagram showing an example of the configuration of the twist angle control section of the second embodiment. FIG. 34 is a block diagram showing a configuration example of a target steering torque generation section according to a modification of the second embodiment. FIG. 35 is a diagram showing an example of the configuration of the SBW system in correspondence with the general configuration of the electric power steering device shown in FIG. 1. In FIG. FIG. 36 is a block diagram showing the configuration of the third embodiment. FIG. 37 is a diagram illustrating a configuration example of a target turning angle generation section. FIG. 38 is a diagram illustrating a configuration example of a steering angle control section. FIG. 39 is a flowchart showing an example of the operation of the third embodiment. FIG. 40 is a block diagram illustrating a configuration example of a low μ road torque correction value calculating section according to the third embodiment. FIG. 41 is a block diagram showing a configuration example of a low μ road torque correction value calculating section according to a modification of the third embodiment.

Hereinafter, modes for carrying out the invention (hereinafter referred to as embodiments) will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments described below. Furthermore, the constituent elements in the embodiments below include those that can be easily imagined by those skilled in the art, those that are substantially the same, and those that are within the so-called equivalent range. Furthermore, the components disclosed in the embodiments below can be combined as appropriate.

(Embodiment 1)
FIG. 1 is a diagram showing a general configuration of an electric power steering device. An electric power steering system (EPS), which is one of the steering systems for a vehicle, consists of a column shaft (steering shaft, steering wheel shaft) 2 of a steering wheel 1, a speed reduction mechanism 3, and a universal joint in the order in which the force applied by the steerer is transmitted. 4a, 4b, pinion rack mechanism 5, tie rods 6a, 6b, and further connected to steering wheels 8L, 8R via hub units 7a, 7b. Further, the column shaft 2 having a torsion bar is provided with a torque sensor 10 for detecting the steering torque Ts of the handle 1 and a steering angle sensor 14 for detecting the steering angle θh. 20 is connected to the column shaft 2 via the speed reduction mechanism 3. A control unit (ECU) 30 that controls the electric power steering device is supplied with electric power from the battery 13 and also receives an ignition key signal via the ignition key 11 . The control unit 30 calculates a current command value of an assist (steering assist) command based on the steering torque Ts detected by the torque sensor 10 and the vehicle speed Vs detected by the vehicle speed sensor 12, and compensates the current command value. The current supplied to the motor 20 is controlled by the voltage control command value Vref.

The control unit 30 is connected to an in-vehicle network such as a CAN (Controller Area Network) 40 that exchanges various information about the vehicle. Furthermore, a non-CAN 41 for transmitting and receiving communications other than the CAN 40, analog/digital signals, radio waves, etc. can also be connected to the control unit 30.

The control unit 30 is mainly composed of a CPU (including an MCU, an MPU, etc.). FIG. 2 is a schematic diagram showing the hardware configuration of a control unit that controls the electric power steering device.

A control computer 1100 configuring the control unit 30 includes a CPU (Central Processing Unit) 1001, a ROM (Read Only Memory) 1002, a RAM (Random Access Memory) 1003, an EEPROM (Electrically Erasable Programmable ROM) 1004, and an interface (I/F). ) 1005, an A/D (Analog/Digital) converter 1006, a PWM (Pulse Width Modulation) controller 1007, and the like, which are connected to a bus.

The CPU 1001 is a processing device that executes a computer program for controlling the electric power steering apparatus (hereinafter referred to as a control program) to control the electric power steering apparatus.

ROM 1002 stores a control program for controlling the electric power steering device. Further, the RAM 1003 is used as a work memory for operating a control program. The EEPROM 1004 stores control data and the like that are input and output by the control program. The control data is used on a control computer program developed in the RAM 1003 after the control unit 30 is powered on, and is overwritten in the EEPROM 1004 at a predetermined timing.

The ROM 1002, RAM 1003, EEPROM 1004, etc. are storage devices that store information, and are storage devices (primary storage devices) that can be directly accessed by the CPU 1001.

The A/D converter 1006 inputs signals such as the steering torque Ts, the detected current value Im of the motor 20, and the steering angle θh, and converts them into digital signals.

Interface 1005 is connected to CAN 40. The interface 1005 is for receiving a vehicle speed V signal (vehicle speed pulse) from the vehicle speed sensor 12.

The PWM controller 1007 outputs PWM control signals for each UVW phase based on the current command value for the motor 20.

FIG. 3 is a diagram showing an example of an internal block configuration of a control unit in an electric power steering device. The steering torque Ts and the vehicle speed Vs are input to the current command value calculation section 31. The current command value calculation unit 31 refers to a pre-stored lookup table (assist map, etc.) based on the steering torque Ts and the vehicle speed Vs, and calculates a current command value Iref1 which is a control target value for the current supplied to the motor 20. Calculate.

Compensation signal generation section 34 generates compensation signal CM. The compensation signal generation section 34 includes a convergence estimation section 341 , an inertia estimation section 342 , and a self-aligning torque (SAT) estimation section 343 . The convergence estimation unit 341 estimates the yaw rate of the vehicle based on the angular velocity of the motor 20, and estimates a compensation value that improves the yaw convergence of the vehicle by braking the swinging motion of the steering wheel 1. The inertia estimation unit 342 estimates the inertia force of the motor 20 based on the angular acceleration of the motor 20, and estimates a compensation value for compensating the inertia force of the motor 20 in order to improve responsiveness. The SAT estimation unit 343 estimates the self-aligning torque _TSAT based on the steering torque Ts, the assist torque, and the angular velocity and angular acceleration of the motor 20, and calculates a compensation value for compensating the assist torque using the self-aligning torque as a reaction force. presume. In addition to the convergence estimation section 341, the inertia estimation section 342, and the SAT estimation section 343, the compensation signal generation section 34 may include an estimation section that estimates other compensation values. The compensation signal CM is obtained by adding the compensation value of the inertia estimation section 342 and the compensation value of the SAT estimation section 343 in the addition section 344, and adding this added value and the compensation value of the convergence estimation section 341 in the addition section 345. This is the added value. Note that in the present disclosure, the self-aligning torque T _SAT estimated by the SAT estimation unit 343 is also output to the target steering torque generation unit 200 described later.

In the adder 32A, the compensation signal CM from the compensation signal generator 34 is added to the current command value Iref1, and by adding the compensation signal CM, the characteristics of the steering system are compensated for the current command value Iref1, and the convergence and It is designed to improve inertial characteristics, etc. Then, the current command value Iref1 passes through the adding section 32A to become the characteristic-compensated current command value Iref2, and the current command value Iref2 is input to the current limiting section 33. In the current limiter 33, the maximum current of the current command value Iref2 is limited, and a current command value Irefm is generated. The current command value Irefm is input to the subtraction unit 32B, and the deviation I (Irefm−Im) from the current detection value Im fed back from the motor 20 side is calculated by the subtraction unit 32B. The deviation I is input to the PI control unit 35 for improving the characteristics of the steering operation. Then, the voltage control command value Vref whose characteristics have been improved by the PI control section 35 is input to the PWM control section 36, and the motor 20 is further PWM-driven via the inverter circuit 37 as a motor drive section. The detected current value Im of the motor 20 is detected by the current detector 38 and fed back to the subtraction unit 32B. Further, the inverter circuit 37 uses a field effect transistor (hereinafter referred to as FET) as a driving element, and is configured as a bridge circuit of the FET.

In assist control in conventional electric power steering devices, a torque sensor detects the steering torque manually input by the driver as the torsion torque of the torsion bar, and the motor current is mainly used as an assist current corresponding to that torque. It's in control. However, when controlling with this method, the steering torque may vary depending on the steering angle due to differences in road surface conditions (for example, slope). Variations in motor output characteristics due to aging may also affect the steering torque.

FIG. 4 is a structural diagram showing an example of installing a steering angle sensor.

The column shaft 2 is equipped with a torsion bar 2A. Road surface reaction force Rr and road surface information (road surface frictional resistance μ) act on the steering wheels 8L and 8R. An upper angle sensor is provided on the handle side of the column shaft 2 across the torsion bar 2A. A lower angle sensor is provided on the steering wheel side of the column shaft 2 across the torsion bar 2A. The upper angle sensor detects the steering wheel angle θ ₁ and the lower angle sensor detects the column angle θ ₂ . The steering angle θh is detected by a steering angle sensor provided at the top of the column shaft 2. The torsion angle Δθ of the torsion bar is expressed by the following equation (1) from the deviation of the handle angle θ ₁ and the column angle θ ₂ . Further, the torsion bar torque Tt is expressed by the following equation (2) using the torsion angle Δθ of the torsion bar expressed by the equation (1). Note that Kt is a spring constant of the torsion bar 2A.

Δθ=θ ₂ −θ ₁ ...(1)

Tt=-Kt×Δθ...(2)

Torsion bar torque Tt can also be detected using a torque sensor. In this embodiment, the torsion bar torque Tt is also treated as the steering torque Ts.

FIG. 5 is a diagram showing an example of an internal block configuration of the control unit according to the first embodiment.

The control unit 30 includes a target steering torque generation section 200, a torsion angle control section 300, a steering direction determination section 400, and a conversion section 500 as internal block configurations.

In this embodiment, the driver's steering is assisted and controlled by the motor 20 of the EPS steering system/vehicle system 100. The EPS steering system/vehicle system 100 includes, in addition to the motor 20, an angle sensor, an angular velocity calculation section, and the like.

Target steering torque generation unit 200 generates target steering torque Tref, which is a target value of steering torque when assist-controlling the steering system of a vehicle in the present disclosure. The converter 500 converts the target steering torque Tref into a target twist angle Δθref. The torsion angle control unit 300 generates a motor current command value Iref, which is a control target value for the current supplied to the motor 20.

The torsion angle control unit 300 calculates a motor current command value Iref such that the torsion angle Δθ becomes the target torsion angle Δθref. Motor 20 is driven by motor current command value Iref.

The steering direction determination unit 400 determines whether the steering direction is right or left based on the motor angular velocity ωm output from the EPS steering system/vehicle system 100, and outputs the determination result as a steering state signal STs. FIG. 6 is an explanatory diagram of the steering direction.

The steering state indicating whether the steering direction is right or left can be determined, for example, from the relationship between the steering angle θh and the motor angular velocity ωm as shown in FIG. That is, when the motor angular velocity ωm is a positive value, it is determined that the motor is turning to the right, and when the motor angular velocity ωm is a negative value, it is determined that the motor is turning to the left. Note that instead of the motor angular velocity ωm, an angular velocity calculated by performing velocity calculation on the steering angle θh, the steering wheel angle θ ₁ or the column angle θ ₂ may be used.

The conversion unit 500 converts the target steering torque Tref generated by the target steering torque generation unit 200 into a target torsion angle Δθref using the relationship in equation (2) above.

Next, a basic operation example of the control unit of the first embodiment will be described. FIG. 7 is a flowchart showing an example of the operation of the control unit according to the first embodiment.

The steering direction determining unit 400 determines whether the steering direction is right or left based on the sign of the motor angular velocity ωm output from the EPS steering system/vehicle system 100, and uses the determination result as a steering state signal STs to determine the target steering. It outputs to the torque generation section 200 (step S10).

The target steering torque generation unit 200 generates a target steering torque Tref based on the vehicle speed Vs, the vehicle speed determination signal Vfail, the steering state signal STs, the steering angle θh, and the actual yaw rate γre (step S20).

The converter 500 converts the target steering torque Tref generated by the target steering torque generator 200 into a target twist angle Δθref (step S20). The target twist angle Δθref is output to the twist angle control section 300.

The torsion angle control unit 300 calculates the motor current command value Iref based on the target torsion angle Δθref, the steering angle θh, the torsion angle Δθ, and the motor angular velocity ωm (step S30).

Then, current control is performed based on the motor current command value Iref output from the twist angle control section 300, and the motor 20 is driven (step S40).

FIG. 8 is a block diagram illustrating a configuration example of the target steering torque generation section of the first embodiment. As shown in FIG. 8, the target steering torque generation section 200 includes a basic map section 210, a multiplication section 211, a sign extraction section 213, a differentiation section 220, a damper gain map section 230, a hysteresis correction section 240, a SAT information correction section 250, It includes a multiplication section 260, addition sections 261, 262, 263, and a low μ road torque correction value calculation section 280. FIG. 9 is a diagram showing an example of the characteristics of the basic map held by the basic map section. FIG. 10 is a diagram illustrating an example of the characteristics of a damper gain map held by the damper gain map section.

The basic map section 210 receives the steering angle θh and the vehicle speed Vs. The basic map unit 210 uses the basic map shown in FIG. 9 to output a torque signal Tref_a0 using the vehicle speed Vs as a parameter. That is, the basic map section 210 outputs the torque signal Tref_a0 according to the vehicle speed Vs.

As shown in FIG. 9, the torque signal Tref_a0 has a characteristic that increases as the magnitude (absolute value) |θh| of the steering angle θh increases. Furthermore, the torque signal Tref_a has a characteristic of increasing as the vehicle speed Vs increases. In addition, in FIG. 9, a map is constructed according to the magnitude |θh| of the steering angle θh, but a map according to the positive and negative steering angles θh may be constructed. In this case, the value of the torque signal Tref_a0 can take positive or negative values. Therefore, it is necessary to appropriately change the configuration of the low μ road torque correction value calculating section that calculates the correction value for the torque signal Tref_a0. In the following description, a mode will be described in which the torque signal Tref_a0, which is a positive value corresponding to the magnitude |θh| of the steering angle θh shown in FIG. 9, is output.

The code extraction unit 213 extracts the code of the steering angle θh. Specifically, for example, the value of the steering angle θh is divided by the absolute value of the steering angle θh. Thereby, the sign extraction unit 213 outputs "1" when the sign of the steering angle θh is "+", and outputs "-1" when the sign of the steering angle θh is "-".

The steering angle θh is input to the differentiator 220. The differentiator 220 differentiates the steering angle θh to calculate the steering angular velocity ωh, which is angular velocity information. The differentiator 220 outputs the calculated steering angular velocity ωh to the multiplier 260.

The vehicle speed Vs is input to the damper gain map section 230. The damper gain map section 230 uses a vehicle speed sensitive damper gain map shown in FIG. 10 to output a damper gain _DG according to the vehicle speed Vs.

As shown in FIG. 10, the damper gain _DG has a characteristic of gradually increasing as the vehicle speed Vs increases. The damper gain _DG may be varied in accordance with the steering angle θh.

The multiplier 260 multiplies the steering angular velocity ωh output from the differentiator 220 by the damper gain _DG output from the damper gain map section 230, and outputs the result to the adder 262 as a torque signal Tref_b.

The steering direction determination unit 400 performs determination as shown in FIG. 6, for example. The steering angle θh, the vehicle speed Vs, and the steering state signal STs, which is the determination result shown in FIG. 6, are input to the hysteresis correction unit 240. The hysteresis correction unit 240 calculates the torque signal Tref_c using the following equations (3) and (4) based on the steering angle θh and the steering state signal STs. Note that in the following equations (3) and (4), x is the steering angle θh, y _R =Tref_c and y _L =Tref_c are the torque signal Tref_c. Further, the coefficient a has a value larger than 1, and the coefficient c has a value larger than 0. The coefficient Ahys indicates the output width of the hysteresis characteristic, and the coefficient c is a coefficient indicating the roundness of the hysteresis characteristic.

y _R =Ahys{1-a ^-c(x-b) }...(3)

y _L =-Ahys{1-a ^c(x-b') }...(4)

When steering to the right, the torque signal Tref_c(y _R ) is calculated using the above equation (3). At the time of left-turn steering, the torque signal Tref_c(y _L ) is calculated using the above equation (4). Note that when switching from right-turn steering to left-turn steering or from left-turn steering to right-turn steering, the final coordinates (x ₁ , y ₁ ) of the previous values of the steering angle θh and the torque signal Tref_c are Based on the value of , the coefficient b or b' shown in the following equation (5) or (6) is substituted into the above equations (3) and (4) after the steering switching. This maintains continuity before and after steering switching.

b=x ₁ + (1/c)log _a {1-(y ₁ /Ahys)}...(5)

b'=x ₁ -(1/c)log _a {1-(y ₁ /Ahys)}...(6)

The above equations (5) and (6) can be derived by substituting x ₁ for x and y ₁ for y _R and y _L in the above equations (3) and (4). .

For example, when Napier's number e is used as the coefficient a, the above equations (3), (4), (5), and (6) become the following equations (7), (8), and (9), respectively. ) and (10).

y _R =Ahys[1-exp{-c(x-b)}]...(7)

y _L =-Ahys[{1-exp{c(x-b')}]...(8)

b=x ₁ + (1/c)log _e {1-(y ₁ /Ahys)}...(9)

b'=x ₁ -(1/c)log _e {1-(y ₁ /Ahys)}...(10)

FIG. 11 is a diagram showing an example of the characteristics of the hysteresis correction section. In the example shown in FIG. 11, in the above equations (9) and (10), Ahys = 1 [Nm], c = 0.3, starting from 0 [deg], +50 [deg], -50 An example of the characteristics of the hysteresis-corrected torque signal Tref_c when the steering is performed at [deg] is shown. As shown in FIG. 11, the torque signal Tref_c output from the hysteresis correction unit 240 has a hysteresis characteristic as follows: 0 origin → L1 (thin line) → L2 (broken line) → L3 (thick line).

Note that Ahys, which is a coefficient representing the output width of the hysteresis characteristic, and c, which is a coefficient representing roundness, may be made variable depending on one or both of the vehicle speed Vs and the steering angle θh.

Further, the steering angular velocity ωh is obtained by differential calculation with respect to the steering angle θh, and low-pass filter (LPF) processing is appropriately performed to reduce the influence of high-frequency noise. Further, differential calculation and LPF processing may be performed using a high pass filter (HPF) and gain. Furthermore, the steering angular velocity ωh may be calculated by performing differential calculation and LPF processing on the steering wheel angle θ1 detected by the upper angle sensor or the column angle θ2 detected by the lower angle sensor instead of the steering angle θh. . The motor angular velocity ωm may be used as the angular velocity information instead of the steering angular velocity ωh, and in this case, the differentiator 220 is not required.

FIG. 12 is a block diagram showing an example of the configuration of the low μ road torque correction value calculating section of the first embodiment.

As shown in FIG. 12, the low μ road torque correction value calculation unit 280 receives the torque signal Tref_a0 output from the basic map unit 210 (see FIG. 8) and the torque signal Tref_a0 output from the SAT estimation unit 343 (see FIG. 3). Self-aligning torque _TSAT is input.

FIG. 13 is a diagram showing changes in actual self-aligning torque on a low μ road.

The actual self-aligning torque (also referred to as SAT value) of the tire increases as the magnitude (absolute value) of the steering angle θh increases |θh|. This SAT value is approximately proportional to the torque signal Tref_a0 output from the basic map section 210 in normal driving conditions. Hereinafter, the proportional coefficient of the SAT value with respect to the torque signal Tref_a0 is assumed to be "k". In addition, in the present disclosure, a "normal driving state" refers to a state in which the tires grip the road surface.

On the other hand, as shown in FIG. 13, when the frictional resistance of the road surface is significantly reduced due to, for example, ice burns or hydroplaning in puddles, the tires slip and the SAT value decreases. In the example shown in FIG. 13, when the frictional resistance μ of the road surface is 1.0, the SAT value decreases in the region equal to or greater than the steering angle θb, and when the frictional resistance μ of the road surface is 0.1, the SAT value decreases in the region equal to or greater than the steering angle θa. An example is shown in which the SAT value decreases in the region. In this way, when the frictional resistance μ of the road surface decreases and the tire slips, the torque signal Tref_a0 output from the basic map unit 210 and the value obtained by multiplying the SAT value by the proportionality coefficient k diverge. In other words, if the steering force of the steering wheel is controlled in the same manner as in normal driving conditions even though the tires have lost grip, the driver will not notice that the tires have lost grip and will not be able to perform emergency avoidance maneuvers. may be delayed.

In this embodiment, the driver is enabled to perform an emergency avoidance operation by providing feedback to the driver that the grip force of the tire has been lost based on the physical quantity generated by tire slip. Hereinafter, by using the self-aligning torque _TSAT estimated by the SAT estimator 343 (see FIG. 3) as a physical quantity generated by tire slip, feedback to the driver that the tire grip force has been lost is provided. A configuration that enables this will be explained.

As shown in FIG. 12, the low μ road torque correction value calculation unit 280 of the first embodiment includes a proportional coefficient multiplication unit 281, a subtraction unit 282, a torque adjustment coefficient value mapping unit 283, an absolute value calculation unit 284, including.

The self-aligning torque T _SAT is input to the absolute value calculation unit 284 . The absolute value calculation unit 284 calculates the absolute value |T _SAT | of the input self-aligning torque T _SAT . The proportional coefficient multiplier 281 outputs a value k (|T SAT |) obtained by multiplying the input absolute value of the self-aligning torque |T _SAT | by a predetermined proportional coefficient k (|T _SAT |) to the subtractor 282 . The value of the proportional coefficient k is set to a value such that the torque signal Tref_a0 and the output value k (|T _SAT |) of the proportional coefficient multiplier 281 substantially match under normal running conditions.

The subtraction unit 282 outputs a value Tref_a0−k (|T _SAT |) obtained by subtracting the output value k (|T _SAT |) of the proportional coefficient multiplication unit 281 from the torque signal Tref_a0 to the torque adjustment coefficient value mapping unit 283.

The torque adjustment coefficient value map section 283 holds a torque adjustment coefficient value map showing the relationship between the output value Tref_a0-k (|T _SAT |) of the subtraction section 282 and the torque adjustment coefficient value G. FIG. 14 is a diagram showing an example of the characteristics of the torque adjustment coefficient value map held by the torque adjustment coefficient value map section of the first embodiment.

In the present disclosure, the torque adjustment coefficient value G can take a positive value of 1 or less. As shown in FIG. 14, the torque adjustment coefficient value map subtracts the torque adjustment coefficient value G by "1.0" in the region where the output value Tref_a0-k (|T _SAT |) of the subtraction unit 282 is 0 or more and less than A. An example is shown in which the torque adjustment coefficient value G is set to "0.1" in a region where the output value Tref_a0-k (|T _SAT |) of the section 282 is greater than A and is greater than or equal to B. Further, in the torque adjustment coefficient value map, the torque adjustment coefficient value G ranges from "1.0" to "0.1" in a region where the output value Tref_a0-k (|T _SAT |) of the subtraction unit 282 is greater than or equal to A and less than B. It has the characteristic of gradually decreasing until

Note that the A value and B value of the output value Tref_a0-k (|T _SAT |) of the subtraction unit 282 are set as appropriate. Further, the value of the torque adjustment coefficient value G above the B value of the output value Tref_a0-k (|T _SAT |) of the subtraction unit 282 is one example, and is not limited to this "0.1". These values are preferably values that do not give the driver a sense of discomfort when steering. Further, the torque adjustment coefficient value map may have a curved characteristic instead of a linear characteristic as shown in FIG.

The torque adjustment coefficient value map section 283 uses the torque adjustment coefficient value map shown in FIG. 14 to derive and output the torque adjustment coefficient value G according to the output value Tref_a0-k (|T _SAT |) of the subtraction section 282. do. Note that the torque adjustment coefficient value G may be calculated using a mathematical formula that indicates the relationship between the output value Tref_a0-k (|T _SAT |) of the subtraction unit 282 and the torque adjustment coefficient value G.

Returning to FIG. 8, the multiplication unit 211 calculates the sign of the steering angle θh output from the sign extraction unit 213 and the low μ road torque correction value calculation unit 280 for the torque signal Tref_a0 output from the basic map unit 210. It is multiplied by the output torque adjustment coefficient value G and outputted to the addition section 261 as a torque signal Tref_a. As a result, a torque signal Tref_a corresponding to the positive and negative steering angles θh is obtained.

FIG. 15 is a diagram showing an example of the effect of the torque adjustment coefficient value output from the low μ road torque correction value calculating section. The example shown in FIG. 15 shows a normal driving condition, that is, a state in which the tires grip the road surface until time t, and after time t, it shows that the tire's grip power is gradually lost. There is.

In FIG. 15, until time t, the torque signal Tref_a0 and the output value k (|T _SAT |) of the proportional coefficient multiplier 281 substantially match, as shown by the solid line in the diagram (solid line in the diagram). . At this time, the output value Tref_a0-k (|T _SAT |) of the subtraction unit 282 is less than or equal to A, and the torque adjustment coefficient value G at this time is "1.0" (see FIG. 14).

On the other hand, in FIG. 15, after time t, the difference between the torque signal Tref_a0 indicated by the solid line in the figure and the output value k (|T _SAT |) of the proportional coefficient multiplier 281 indicated by the dashed line in the figure gradually increases. growing. At this time, the output value Tref_a0-k (|T _SAT |) of the subtraction unit 282 gradually increases from A. The torque adjustment coefficient value G at this time gradually decreases from "1.0" (see FIG. 14). Therefore, as shown by the broken line in the figure, the torque signal Tref_a becomes smaller than in the normal running state (solid line in the figure). This makes the steering feel lighter than in normal driving conditions, allowing the driver to recognize that the tires have lost grip, and allowing him to perform appropriate emergency avoidance maneuvers.

The torsion angle control section 300 (see FIG. 5) of the first embodiment will be described below with reference to FIG. 16.

FIG. 16 is a block diagram showing an example of the configuration of the twist angle control section of the first embodiment. The torsion angle control unit 300 calculates a motor current command value Iref based on the target torsion angle Δθref, the torsion angle Δθ, the steering angle θh, and the motor angular velocity ωm. The torsion angle control section 300 includes a torsion angle feedback (FB) compensation section 310, a speed control section 330, a stabilization compensation section 340, an output restriction section 350, a steering angle disturbance compensation section 360, a subtraction section 361, an addition section 363, and a deceleration section. A ratio section 370 is provided.

The target torsion angle Δθref output from the conversion section 500 is added and input to the subtraction section 361. The twist angle Δθ is subtracted and input to the subtractor 361. The steering angle θh is input to the steering angle disturbance compensator 360. The motor angular velocity ωm is input to the stabilization compensator 340.

The torsion angle FB compensation unit 310 multiplies the deviation Δθ0 between the target torsion angle Δθref and the torsion angle Δθ calculated by the subtraction unit 361 by a compensation value CFB (transfer function), so that the torsion angle Δθ follows the target torsion angle Δθref. A target column angular velocity ωref1 such that The target column angular velocity ωref1 is added and output to the adding section 363. The compensation value CFB may be a simple gain Kpp or a commonly used compensation value such as a compensation value for PI control.

The steering angle disturbance compensator 360 multiplies the steering angle θh by a compensation value Ch (transfer function) and outputs a target column angular velocity ωref2. The target column angular velocity ωref2 is added and output to the adding section 363.

Adding section 363 adds target column angular velocity ωref1 and target column angular velocity ωref2, and outputs the result to speed control section 330 as target column angular velocity ωref. Thereby, it is possible to suppress the influence on the torsion bar torsion angle Δθ due to a change in the steering angle θh input by the driver, and improve the followability of the torsion angle Δθ to the target torsion angle Δθref in response to sudden steering.

When the steering angle θh changes due to the driver's steering, the change in the steering angle θh affects the torsion angle Δθ as a disturbance, causing a deviation from the target torsion angle Δθref. In particular, in response to sudden steering, the deviation from the target torsion angle Δθref due to changes in the steering angle θh becomes noticeable. The basic purpose of the steering angle disturbance compensator 360 is to reduce the influence of the steering angle θh as this disturbance.

The speed control unit 330 calculates a motor current command value Is such that the column angular velocity ωc follows the target column angular velocity ωref by IP control (proportional advance type PI control). The column angular velocity ωc may be a value obtained by multiplying the motor angular velocity ωm by the reduction ratio 1/N of the reduction ratio section 370, which is a reduction mechanism, as shown in FIG. 16.

The subtraction unit 333 calculates the difference (ωref−ωc) between the target column angular velocity ωref and the column angular velocity ωc. Integrating section 331 integrates the difference (ωref - ωc) between target column angular velocity ωref and column angular velocity ωc, and adds and inputs the integration result to subtracting section 334 .

The torsional angular velocity ωt is also output to the proportional section 332. The proportional section 332 performs proportional processing on the column angular velocity ωc using a gain Kvp, and subtracts and inputs the proportional processing result to the subtracting section 334 . The subtraction result in the subtraction unit 334 is output as a motor current command value Is. Note that the speed control unit 330 performs not IP control but PI control, P (proportional) control, PID (proportional-integral-derivative) control, PI-D control (differential-preceding PID control), model matching control, and model norm. The motor current command value Is may be calculated using a commonly used control method such as control.

The output limiter 350 has an upper limit value and a lower limit value set in advance for the motor current command value Is. The upper and lower limits of the motor current command value Is are limited, and the motor current command value Iref is output.

Note that the configuration of the twist angle control section 300 in this embodiment is merely an example, and may have a configuration different from the configuration shown in FIG. 16. For example, the torsion angle control section 300 may have a configuration that does not include the steering angle disturbance compensation section 360, the addition section 363, or the reduction ratio section 370.

(Modification 1)
FIG. 17 is a block diagram illustrating a configuration example of the target steering torque generation section of Modification 1 of Embodiment 1. FIG. 18 is a block diagram illustrating a configuration example of the low μ road torque correction value calculating section of Modification 1 of Embodiment 1. Note that the same components as those in the first embodiment described above are given the same reference numerals and redundant explanations will be omitted.

As shown in FIG. 17, the target steering torque generation section 200a includes a subtraction section 212 instead of the multiplication section 211. Further, the target steering torque generation section 200a includes a multiplication section 214.

As shown in FIGS. 17 and 18, the low μ road torque correction value calculation unit 280a receives the torque signal Tref_a0 output from the basic map unit 210 and the self-value output from the SAT estimation unit 343 (see FIG. 3). In addition to the lining torque _TSAT , the vehicle speed Vs is input.

As shown in FIG. 18, the low μ road torque correction value calculation unit 280a of the first modification of the first embodiment includes a proportional coefficient multiplication unit 281a, a subtraction unit 282a, a torque adjustment subtraction value mapping unit 283a, and an absolute value calculation unit 280a. 284a.

The self-aligning torque _TSAT is input to the absolute value calculation section 284a. The absolute value calculation unit 284a calculates the absolute value |T _SAT | of the input self-aligning torque T _SAT . The proportional coefficient multiplier 281a outputs a value k (|T SAT |) obtained by multiplying the absolute value |T _SAT | of the input self-aligning torque T _SAT by a predetermined proportional coefficient k (|T _SAT |) to the subtractor 282a. . The value of the proportional coefficient k is set to a value such that the torque signal Tref_a0 and the output value k (|T _SAT |) of the proportional coefficient multiplier 281a substantially match under normal running conditions.

The subtraction unit 282a outputs a value Tref_a0-k (|T _SAT |) obtained by subtracting the output value k (|T _SAT |) of the proportional coefficient multiplication unit 281a from the torque signal Tref_a0 to the torque adjustment subtraction value mapping unit 283a.

The torque adjustment subtraction value map section 283a holds a torque adjustment subtraction value map showing the relationship between the output value Tref_a0-k (|T _SAT |) of the subtraction section 282a, the torque adjustment subtraction value S, and the vehicle speed Vs. FIG. 19 is a diagram illustrating a characteristic example of the torque adjustment subtraction value map held by the torque adjustment subtraction value map section of Modification 1 of Embodiment 1.

As shown in FIG. 19, the torque adjustment subtraction value map sets the torque adjustment subtraction value S to "0" in a region where the output value Tref_a0-k (|T _SAT |) of the subtraction unit 282a is 0 or more and less than A; In the region where the output value Tref_a0-k (|T _SAT |) is greater than A and is greater than or equal to B, an example is shown in which the torque adjustment subtraction value S is set to a constant value according to the vehicle speed Vs. Furthermore, the torque adjustment subtraction value map has a characteristic in which the torque adjustment subtraction value S gradually increases from "0" in a region where the output value Tref_a0-k (|T _SAT |) of the subtraction unit 282a is greater than or equal to A and less than B. are doing.

Note that the A value and B value of the output value Tref_a0-k (|T _SAT |) of the subtraction unit 282a are set as appropriate. Further, the value of the torque adjustment subtraction value S when the output value Tref_a0-k (|T _SAT |) of the subtraction unit 282a is equal to or greater than the A value is set to a value that does not exceed the magnitude of the torque signal Tref_a0 that changes depending on the vehicle speed Vs. be done. These values are preferably values that do not give the driver a sense of discomfort when steering. Further, the torque adjustment subtraction value map may have a curved characteristic instead of a linear characteristic as shown in FIG.

The torque adjustment subtraction value map section 283a uses the torque adjustment subtraction value map shown in FIG. 19 to derive and output a torque adjustment subtraction value S according to the output value Tref_a0-k (|T _SAT |) of the subtraction section 282a. do. Note that the torque adjustment subtraction value S may be calculated using a mathematical formula showing the relationship between the output value Tref_a0-k (|T _SAT |) of the subtraction unit 282a, the torque adjustment subtraction value S, and the vehicle speed Vs. .

Returning to FIG. 17, the subtraction unit 212 subtracts the torque adjustment subtraction value S output from the low μ road torque correction value calculation unit 280a from the torque signal Tref_a0 output from the basic map unit 210. The multiplication unit 214 multiplies the output value of the subtraction unit 212 by the sign of the steering angle θh output from the sign extraction unit 213, and outputs the result to the addition unit 261 as a torque signal Tref_a. As a result, a torque signal Tref_a corresponding to the positive and negative steering angles θh is obtained.

Also in the configuration of the first modification of the first embodiment shown in FIGS. 17 and 18, similarly to the configuration according to the first embodiment described above, in a state where the grip force of the tire is lost, the torque signal Tref_a is changed to the normal driving state. (solid line in FIG. 15) (broken line in FIG. 15). This makes the steering feel lighter than in normal driving conditions, allowing the driver to recognize that the tires have lost grip, and allowing him to perform appropriate emergency avoidance maneuvers.

(Modification 2)
FIG. 20 is a diagram illustrating an example of an internal block configuration of a control unit according to Modification 2 of Embodiment 1. FIG. 21 is a block diagram illustrating a configuration example of a target steering torque generation section of a second modification of the first embodiment. FIG. 22 is a block diagram illustrating a configuration example of the low μ road torque correction value calculating section of the second modification of the first embodiment. Note that the same components as those in the first embodiment described above are given the same reference numerals and redundant explanations will be omitted.

In the configuration of the second modification of the first embodiment, as shown in FIG. 20, the actual yaw rate γ detected by the yaw rate sensor 15 (see FIG. 1) is input to the target steering torque generation unit 200b. In a second modification of the first embodiment, a configuration will be described in which, by using the actual yaw rate γ as a physical quantity generated by tire slip, it is possible to provide feedback to the driver that the tire grip force has been lost.

As shown in FIGS. 21 and 22, the low μ road torque correction value calculation unit 280b receives the torque signal Tref_a0 output from the basic map unit 210 and the self-value output from the SAT estimation unit 343 (see FIG. 3). Instead of the lining torque _TSAT , the actual yaw rate γ is input.

As shown in FIG. 22, the low μ road torque correction value calculation unit 280b of the second modification of the first embodiment includes a proportional coefficient multiplication unit 281b, a subtraction unit 282b, a torque adjustment coefficient value mapping unit 283b, and an absolute value calculation unit 280b. 284b.

The actual yaw rate γ is input to the absolute value calculation unit 284b. The absolute value calculation unit 284b calculates the absolute value |γ| of the input actual yaw rate γ. The proportional coefficient multiplier 281b multiplies the input absolute value |γ| of the actual yaw rate by a predetermined proportional coefficient k' and outputs a value k'|γ| to the subtracter 282b. The value of the proportional coefficient k' is set to a value such that the torque signal Tref_a0 and the output value k'|γ| of the proportional coefficient multiplier 281b substantially match under normal running conditions.

The subtraction unit 282b outputs a value Tref_a0−k|γ| obtained by subtracting the output value k'|γ| of the proportional coefficient multiplication unit 281b from the torque signal Tref_a0 to the torque adjustment coefficient value mapping unit 283b.

The torque adjustment coefficient value map section 283b holds a torque adjustment coefficient value map showing the relationship between the output value Tref_a0-k'|γ| of the subtraction section 282b and the torque adjustment coefficient value G. The characteristics of the torque adjustment coefficient value map according to the second modification of the first embodiment are similar to the torque adjustment coefficient value map held by the torque adjustment coefficient value map section 283 of the first embodiment shown in FIG. This can be handled by replacing the output value Tref_a0-k (|T _SAT |) with the output value Tref_a0-k'|γ| of the subtraction unit 282b.

The torque adjustment coefficient value map section 283b derives and outputs the torque adjustment coefficient value G according to the output value Tref_a0-k'|γ| of the subtraction section 282b using the torque adjustment coefficient value map described above. Note that the torque adjustment coefficient value G may be calculated using a mathematical formula that indicates the relationship between the output value Tref_a0-k'|γ| of the subtraction unit 282b and the torque adjustment coefficient value G.

Returning to FIG. 21, the multiplication unit 211 uses the sign of the steering angle θh output from the sign extraction unit 213 and the low μ road torque correction value calculation unit 280b for the torque signal Tref_a0 output from the basic map unit 210. It is multiplied by the output torque adjustment coefficient value G and outputted to the addition section 261 as a torque signal Tref_a. As a result, a torque signal Tref_a corresponding to the positive and negative steering angles θh is obtained.

In the configuration of the second modification of the first embodiment shown in FIGS. 20 to 22, similarly to the configuration according to the first embodiment described above, in a state where the grip force of the tire is lost, the torque signal Tref_a is changed to the normal driving state. (solid line in FIG. 15) (broken line in FIG. 15). This makes the steering feel lighter than in normal driving conditions, allowing the driver to recognize that the tires have lost grip, and allowing him to perform appropriate emergency avoidance maneuvers.

(Modification 3)
FIG. 23 is a block diagram illustrating a configuration example of the target steering torque generation section of the third modification of the first embodiment. FIG. 24 is a block diagram illustrating a configuration example of the low μ road torque correction value calculating section of the third modification of the first embodiment. Note that the same components as those in the second modification of the first embodiment described above are given the same reference numerals, and redundant explanations will be omitted.

As shown in FIG. 23, the target steering torque generation section 200c includes a subtraction section 212 instead of the multiplication section 211.

As shown in FIGS. 23 and 24, the low μ road torque correction value calculation unit 280c receives the torque signal Tref_a0 output from the basic map unit 210 and the actual yaw rate γ detected by the yaw rate sensor 15 (see FIG. 1). In addition, vehicle speed Vs is input.

As shown in FIG. 24, the low μ road torque correction value calculation unit 280c of the first modification of the first embodiment includes a proportional coefficient multiplication unit 281c, a subtraction unit 282c, a torque adjustment subtraction value mapping unit 283c, and an absolute value calculation unit 280c. 284c.

The actual yaw rate γ is input to the absolute value calculation unit 284c. The absolute value calculation unit 284c calculates the absolute value |γ| of the input actual yaw rate γ. The proportional coefficient multiplier 281c outputs a value k'|γ| obtained by multiplying the input absolute value |γ| of the actual yaw rate by a predetermined proportional coefficient k' to the subtracter 282c. The value of the proportional coefficient k' is set to a value such that the torque signal Tref_a0 and the output value k'|γ| of the proportional coefficient multiplier 281c substantially match under normal running conditions.

The subtraction unit 282c outputs a value Tref_a0-k'|γ| obtained by subtracting the output value k'γ of the proportional coefficient multiplication unit 281c from the torque signal Tref_a0 to the torque adjustment subtraction value mapping unit 283c.

The torque adjustment subtraction value map section 283c holds a torque adjustment subtraction value map showing the relationship between the output value Tref_a0-k'|γ| of the subtraction section 282c, the torque adjustment subtraction value S, and the vehicle speed Vs. The characteristics of the torque adjustment subtraction value map according to the third modification of the first embodiment are similar to the torque adjustment subtraction value map held by the torque adjustment subtraction value map section 283a of the first modification of the first embodiment shown in FIG. This can be handled by replacing the output value Tref_a0-k (|T _SAT |) of the subtraction unit 282a with the output value Tref_a0-k′|γ| of the subtraction unit 282c.

The torque adjustment subtraction value map section 283c uses the above-described torque adjustment subtraction value map to derive and output a torque adjustment subtraction value S according to the output value Tref_a0-k'|γ| of the subtraction section 282c. Note that the torque adjustment subtraction value S may be calculated using a mathematical formula showing the relationship between the output value Tref_a0-k'|γ| of the subtraction unit 282c, the torque adjustment subtraction value S, and the vehicle speed Vs.

Returning to FIG. 23, the subtraction unit 212 subtracts the torque adjustment subtraction value S output from the low μ road torque correction value calculation unit 280c from the torque signal Tref_a0 output from the basic map unit 210. The multiplication unit 214 multiplies the output value of the subtraction unit 212 by the sign of the steering angle θh output from the sign extraction unit 213, and outputs the result to the addition unit 261 as a torque signal Tref_a. As a result, a torque signal Tref_a corresponding to the positive and negative steering angles θh is obtained.

In the configuration of the third modification of the first embodiment shown in FIGS. 23 and 24, similarly to the configuration according to the first embodiment described above, the torque signal Tref_a is changed to the normal driving state when the grip force of the tire is lost. (solid line in FIG. 15) (broken line in FIG. 15). This makes the steering feel lighter than in normal driving conditions, allowing the driver to recognize that the tires have lost grip, and allowing him to perform appropriate emergency avoidance maneuvers.

In Embodiment 1 and Modifications 1 to 3 described above, the self-aligning torque T _SAT estimated by the SAT estimation unit 343 (see FIG. 3) and the yaw rate sensor 15 ( For example, a configuration using the actual yaw rate γ detected by the lateral acceleration sensor 16 (see FIG. 1) as a physical quantity generated by tire slip may also be used. Also, the same effects as those of the first embodiment and the first to third variations thereof described above can be obtained.

(Embodiment 2)
FIG. 25 is a diagram illustrating an example of an internal block configuration of a control unit according to the second embodiment. Note that the same components as those described in the first embodiment described above are given the same reference numerals and redundant explanations will be omitted. A control unit (ECU) 30a according to the second embodiment is different from the first embodiment in the configurations of a target steering torque generation section 201 and a torsion angle control section 300a.

In addition to the steering angle θh, vehicle speed Vs, and vehicle speed determination signal Vfail, the steering torque Ts and motor angle θm are input to the target steering torque generation unit 201.

The twist angle control unit 300a calculates a motor current command value Imc such that the twist angle Δθ becomes the target twist angle Δθref. Motor 20 is driven by motor current command value Imc.

FIG. 26 is a block diagram illustrating a configuration example of the target steering torque generation section of the second embodiment. As shown in FIG. 26, the target steering torque generation section 201 of the second embodiment includes a SAT information correction section 250 and an addition section 263 in addition to the configuration described in the first embodiment.

The SAT information correction unit 250 receives the steering angle θh, vehicle speed Vs, steering torque Ts, motor angle θm, and motor current command value Imc. The SAT information correction unit 250 calculates self-aligning torque (SAT) based on the steering torque Ts, motor angle θm, and motor current command value Imc, and further performs filter processing, gain multiplication, and limiting processing to obtain a torque signal ( 1st torque signal) Tref_d is calculated.

FIG. 27 is a block diagram showing an example of the configuration of the SAT information correction section. The SAT information correction section 250 includes a SAT calculation section 251 , a filter section 252 , a steering torque sensitive gain section 253 , a vehicle speed sensitive gain section 254 , a steering angle sensitive gain section 255 , and a restriction section 256 .

Here, the state of torque generated between the road surface and the steering wheel will be explained with reference to FIG. 28. FIG. 28 is an image diagram showing the state of torque generated between the road surface and the steering wheel.

A steering torque Ts is generated by the driver steering the steering wheel, and the motor 20 generates an assist torque (motor torque) Tm in accordance with the steering torque Ts. As a result, the wheels are steered and a self-aligning torque _TSAT is generated as a reaction force. At this time, a torque that acts as a resistance to steering the steering wheel is generated by the column shaft equivalent inertia (inertia acting on the column shaft by the motor 20 (rotor), deceleration mechanism, etc.) J and friction (static friction) Fr. Furthermore, the rotational speed of the motor 20 generates a physical torque (viscous torque) expressed as a damper term (damper coefficient _DM ). From the balance of these forces, the equation of motion shown in equation (12) below is obtained.

J×α _M +Fr×sign(ω _M )+D _M ×ω _M =Tm+Ts+T _SAT ...(12)

In the above equation (12), ω _M is the motor angular velocity converted to the column axis (converted to a value for the column axis), and α _M is the motor angular acceleration converted to the column axis. Then, when the above equation (12) is solved for T _SAT , the following equation (13) is obtained.

T _SAT = -Tm - Ts + J × α _M + Fr × sign (ω _M ) + D _M × ω _M (13)

As can be seen from the above equation (13), by predetermining the column shaft converted inertia J, static friction Fr, and damper coefficient DM as constants, the motor angular velocity ω _M , motor angular acceleration α _M , assist torque Tm, and steering torque Ts Thus, the self-aligning torque _TSAT can be calculated. Note that the column shaft converted inertia J may be a value simply converted to the column shaft using a relational expression between the motor inertia and the reduction ratio.

The SAT calculation unit 251 receives the steering torque Ts, motor angle θm, and motor current command value Imc. The SAT calculation unit 251 calculates the self-aligning torque T _SAT using the above equation (13). The SAT calculation unit 251 includes a conversion unit 251A, an angular velocity calculation unit 251B, an angular acceleration calculation unit 251C, a block 251D, a block 251E, a block 251F, a block 251G, and adders 251H, 251I, and 251J.

The motor current command value Imc is input to the conversion unit 251A. The conversion unit 251A calculates the column shaft converted assist torque Tm by multiplying by a predetermined gear ratio and torque constant.

The motor angle θm is input to the angular velocity calculation unit 251B. The angular velocity calculation unit 251B calculates the column axis converted motor angular velocity ω _M by differential processing and multiplication by the gear ratio.

Motor angular velocity ω _M is input to the angular acceleration calculation unit 251C. The angular acceleration calculation unit 251C differentiates the motor angular velocity ω _M and calculates the column axis converted motor angular acceleration α _M.

Then, using the input steering torque Ts and the calculated assist torque Tm, motor angular velocity ω _M and motor angular acceleration α _M , block 251D, block 251E, block 251F, block 251G, and adders 251H, 251I, 251J, the self-aligning torque T _SAT is calculated based on Equation 8 using the configuration shown in FIG. 27.

The motor angular velocity ω _M output from the angular velocity calculation unit 251B is input to the block 251D. Block 251D functions as a sign function and outputs the sign of the input data.

The motor angular velocity ω _M output from the angular velocity calculation unit 251B is input to the block 251E. Block 251E multiplies the input data by the damper coefficient D _M and outputs the result.

Block 251F multiplies the input data from block 251D by static friction Fr and outputs the result.

The motor angular acceleration α _M output from the angular acceleration calculation unit 251C is input to the block 251G. Block 251G multiplies the input data by column axis conversion inertia J and outputs the result.

Adder 251H adds steering torque Ts and assist torque Tm output from converter 251A.

Adder 251I subtracts the output of block 251G from the output of adder 251H.

Adder 251J adds the output of block 251E and the output of block 251F, and subtracts the output of adder 251I.

With the above configuration, the above equation (13) can be realized. That is, the self-aligning torque T _SAT is calculated by the configuration of the SAT calculation unit 251 shown in FIG. 27 .

Note that if the column angle can be directly detected, the column angle may be used as the angle information instead of the motor angle θm. In this case, column axis conversion becomes unnecessary. Alternatively, instead of the motor angle θm, a signal obtained by converting the motor angular velocity ωm from the EPS steering system/vehicle system 100 into a column axis may be input as the motor angular velocity ω _M , and the differentiation process with respect to the motor angle θm may be omitted. Furthermore, the self-aligning torque T _SAT may be calculated by a method other than the above, and a measured value may be used instead of a calculated value.

In order to utilize the self-aligning torque T _SAT calculated by the SAT calculation unit 251 to appropriately convey the steering feeling to the driver, the filter unit 252 extracts the information to be conveyed from the self-aligning torque T _SAT and calculates the steering feeling. A torque sensitive gain section 253, a vehicle speed sensitive gain section 254, and a steering angle sensitive gain section 255 adjust the amount to be transmitted, and a limiting section 256 adjusts the upper and lower limit values. Note that in the present disclosure, the self-aligning torque T _SAT calculated by the SAT calculation unit 251 is also output to the target steering torque generation unit 201 .

The self-aligning torque T _SAT is input to the filter section 252 from the SAT calculation section 251 . The filter section 252 performs filter processing on the self-aligning torque T _SAT using, for example, a bandpass filter, and outputs SAT information T _ST 1.

The SAT information T _ST 1 and the steering torque Ts output from the filter section 252 are input to the steering torque sensitive gain section 253 . The steering torque sensitive gain section 253 sets a steering torque sensitive gain.

FIG. 29 is a diagram showing an example of the characteristics of the steering torque sensitive gain. As shown in FIG. 29, the steering torque sensitive gain section 253 sets the steering torque sensitive gain so that the sensitivity is high near on-center, which is the straight traveling state. The steering torque sensitive gain section 253 multiplies the SAT information T _ST 1 by a steering torque sensitive gain set according to the steering torque Ts, and outputs the SAT information T _ST 2.

In FIG. 29, the steering torque sensitive gain is fixed at 1.0 when the steering torque Ts is below Ts1 (for example, 2 Nm), and is set to a value smaller than 1.0 when the steering torque Ts is above Ts2 (>Ts1) (for example, 4 Nm). An example is shown in which the steering torque Ts is set to be fixed, and the steering torque Ts is set to decrease at a constant rate between Ts1 and Ts2.

The vehicle speed sensitive gain section 254 receives the SAT information T _ST 2 outputted from the steering torque sensitive gain section 253 and the vehicle speed Vs. Vehicle speed sensitive gain section 254 sets a vehicle speed sensitive gain.

FIG. 30 is a diagram showing an example of the characteristics of the vehicle speed sensitive gain. As shown in FIG. 30, the vehicle speed sensitive gain unit 254 sets the vehicle speed sensitive gain so that the sensitivity is high during high speed driving. The vehicle speed sensitive gain unit 254 multiplies the SAT information T _ST 2 by a vehicle speed sensitive gain set according to the vehicle speed Vs, and outputs the SAT information T _ST 3.

In FIG. 30, the vehicle speed sensitive gain is fixed at 1.0 when the vehicle speed Vs is equal to or higher than Vs2 (for example, 70 km/h), and is a value smaller than 1.0 when the vehicle speed Vs is equal to or lower than Vs1 (<Vs2) (for example, 50 km/h). , and the vehicle speed Vs is set to increase at a constant rate between Vs1 and Vs2.

The SAT information T _ST 3 and the steering angle θh output from the vehicle speed sensitive gain unit 254 are input to the steering angle sensitive gain unit 255 . The steering angle sensitive gain section 255 sets a steering angle sensitive gain.

FIG. 31 is a diagram showing an example of the characteristics of the steering angle sensitive gain. As shown in FIG. 31, the steering angle sensitive gain section 255 starts acting from a predetermined steering angle, and sets the steering angle sensitive gain so that the sensitivity becomes high when the steering angle is large. The steering angle sensitive gain section 255 multiplies the SAT information T _ST 3 by a steering angle sensitive gain set according to the steering angle θh, and outputs a torque signal Tref_d0.

In FIG. 31, the steering angle sensitive gain is a predetermined gain value Gα when the steering angle θh is θh1 (for example, 10 degrees) or less, and is fixed at 1.0 when the steering angle θh is θh2 (for example, 30 degrees) or more. An example is shown in which the values are set to increase at a constant rate between θh1 and θh2. If it is desired to increase the sensitivity when the steering angle θh is large, Gα may be set in the range of 0≦Gα<1. If it is desired to increase the sensitivity when the steering angle θh is small, Gα may be set in the range 1<Gα, although not shown. If you do not want to change the sensitivity depending on the steering angle θh, you may set Gα=1.

The torque signal Tref_d0 output from the steering angle sensitive gain section 255 is input to the limiting section 256. In the limiter 256, an upper limit value and a lower limit value of the torque signal Tref_d0 are set.

FIG. 32 is a diagram showing an example of setting the upper limit value and lower limit value of the torque signal in the limiting section. As shown in FIG. 32, the limiter 256 has an upper limit value and a lower limit value set in advance for the torque signal Tref_d0, and when the input torque signal Tref_d0 is greater than or equal to the upper limit value, the upper limit value is set, and when it is less than or equal to the lower limit value, the limit value is set. The lower limit value is output as the torque signal Tref_d in other cases, and the torque signal Tref_d0 is output as the torque signal Tref_d.

Note that the steering torque sensitive gain, vehicle speed sensitive gain, and steering angle sensitive gain may have curved characteristics instead of linear characteristics as shown in FIGS. 29, 30, and 31. Furthermore, the settings of the steering torque sensitive gain, vehicle speed sensitive gain, and steering angle sensitive gain may be adjusted as appropriate depending on the steering feeling. Furthermore, if there is no risk that the magnitude of the torque signal will increase or if it is suppressed by other means, the limiting section 256 may be deleted. The steering torque sensitive gain section 253, vehicle speed sensitive gain section 254, and steering angle sensitive gain section 255 can also be omitted as appropriate. Furthermore, the installation positions of the steering torque sensitive gain, vehicle speed sensitive gain, and steering angle sensitive gain may be replaced. Alternatively, for example, the steering torque sensitive gain, the vehicle speed sensitive gain, and the steering angle sensitive gain may be obtained in parallel and multiplied by the SAT information T _ST 1 in one component.

That is, the configuration of the SAT information correction unit 250 in this embodiment is an example, and the configuration may be different from the configuration shown in FIG. 27.

Also in this embodiment, the same effects as in the first embodiment can be obtained by configuring the target steering torque generation section 201 to include the low μ road torque correction value calculation section 280 described in the above-mentioned first embodiment. can. Specifically, the self-aligning torque T _SAT calculated by the SAT calculation unit 251 (see FIG. 27) may be input to the low μ road torque correction value calculation unit 280 shown in FIG. 11.

The torsion angle control section 300a of the second embodiment will be described below with reference to FIG. 33.

FIG. 33 is a block diagram showing an example of the configuration of the twist angle control section of the second embodiment. The torsion angle control unit 300a calculates a motor current command value Imc based on the target torsion angle Δθref, the torsion angle Δθ, and the motor angular velocity ωm. The torsion angle control section 300a includes a torsion angle feedback (FB) compensation section 310, a torsion angular velocity calculation section 320, a speed control section 330, a stabilization compensation section 340, an output restriction section 350, a subtraction section 361, and an addition section 362. .

The target torsion angle Δθref output from the conversion section 500 is added and input to the subtraction section 361. The torsion angle Δθ is subtracted and input to the subtraction unit 361 and is also input to the torsion angular velocity calculation unit 320. The motor angular velocity ωm is input to the stabilization compensator 340.

The torsion angle FB compensation unit 310 multiplies the deviation Δθ0 between the target torsion angle Δθref and the torsion angle Δθ calculated by the subtraction unit 361 by a compensation value CFB (transfer function), so that the torsion angle Δθ follows the target torsion angle Δθref. A target torsional angular velocity ωref is output such that The compensation value CFB may be a simple gain Kpp or a commonly used compensation value such as a compensation value for PI control.

The target torsion angular velocity ωref is input to the speed control section 330. The torsion angle FB compensation unit 310 and the speed control unit 330 make it possible to make the torsion angle Δθ follow the target torsion angle Δθref and realize a desired steering torque.

The torsion angular velocity calculation unit 320 performs differential calculation processing on the torsion angle Δθ to calculate the torsion angular velocity ωt. The torsion angular velocity ωt is output to the velocity control section 330. The torsional angular velocity calculating section 320 may perform pseudo-differentiation using the HPF and gain as the differential calculation. Further, the torsion angular velocity calculation unit 320 may calculate the torsion angular velocity ωt by another means or from a method other than the torsion angle Δθ, and output the calculated torsion angular velocity ωt to the speed control unit 330.

The speed control unit 330 calculates a motor current command value Imca1 such that the torsional angular velocity ωt follows the target torsional angular velocity ωref by IP control (proportional advance type PI control).

The subtraction unit 333 calculates the difference (ωref−ωt) between the target torsional angular velocity ωref and the torsional angular velocity ωt. The integrating unit 331 integrates the difference (ωref−ωt) between the target torsional angular velocity ωref and the torsional angular velocity ωt, and inputs the integration result to the subtracting unit 334.

The torsional angular velocity ωt is also output to the proportional section 332. The proportional section 332 performs proportional processing on the torsional angular velocity ωt using a gain Kvp, and subtracts and inputs the proportional processing result to the subtracting section 334 . The subtraction result in the subtraction unit 334 is output as a motor current command value Imca1. Note that the speed control unit 330 performs not IP control but PI control, P (proportional) control, PID (proportional-integral-derivative) control, PI-D control (differential-preceding PID control), model matching control, and model norm. The motor current command value Imca1 may be calculated using a commonly used control method such as control.

The stabilization compensator 340 has a compensation value Cs (transfer function), and calculates a motor current command value Imca2 from the motor angular velocity ωm. If the gains of the torsion angle FB compensator 310 and the speed controller 330 are increased in order to improve the followability and disturbance characteristics, a control-like oscillation phenomenon in the high range will occur. As a countermeasure against this, a transfer function (Cs) necessary for stabilizing the motor angular velocity ωm is set in the stabilization compensator 340. This makes it possible to stabilize the entire EPS control system.

Adding section 362 adds motor current command value Imca1 from speed control section 330 and motor current command value Imca2 from stabilization compensation section 340, and outputs the result as motor current command value Imcb.

The output limiter 350 has an upper limit value and a lower limit value set in advance for the motor current command value Imcb. Output limiting section 350 limits the upper and lower limits of motor current command value Imcb and outputs motor current command value Imc.

Note that the configuration of the torsion angle control section 300a in this embodiment is merely an example, and the configuration may be different from the configuration shown in FIG. 33. For example, the twist angle control section 300a may have a configuration that does not include the stabilization compensation section 340.

(Modified example)
FIG. 34 is a block diagram showing a configuration example of a target steering torque generation section according to a modification of the second embodiment. Note that the same components as those in the second embodiment described above are given the same reference numerals and redundant explanations will be omitted.

As shown in FIG. 34, also in the modification of the second embodiment, the target steering torque generation section 201a is provided with the low μ road torque correction value calculation section 280a described in the first modification of the first embodiment. By doing so, the same effect as the first modification of the first embodiment can be obtained. Specifically, the self-aligning torque T _SAT calculated by the SAT calculation unit 251 (see FIG. 27) may be input to the low μ road torque correction value calculation unit 280a shown in FIG. 17.

In addition, in the above-mentioned embodiment 2 and its modified examples, a configuration using the self-aligning torque T _SAT calculated by the SAT calculation unit 251 (see FIG. 27) was exemplified as the physical quantity generated by tire slip. In this embodiment, as in the second and third variations of the first embodiment, the actual yaw rate γ detected by the yaw rate sensor 15 (see FIG. 1) may be used as the physical quantity generated by tire slip. It is possible. Also, in this embodiment, for example, the actual lateral acceleration detected by the lateral acceleration sensor 16 (see FIG. 1) may be used as the physical quantity caused by tire slip, similar to the first and second embodiments described above. effect can be obtained.

(Embodiment 3)
In the first and second embodiments, the present disclosure is applied to a column-type EPS as one of the vehicle steering devices, but the present disclosure is not limited to an upstream type such as a column type, but is applicable to a downstream type such as a rack and pinion. It is also applicable to EPS. Furthermore, by performing feedback control based on the target torsion angle, it is also applicable to a steer-by-wire (SBW) reaction force device, etc., which includes at least a torsion bar (with an arbitrary spring constant) and a sensor for detecting the torsion angle. An embodiment (Embodiment 3) in which the present disclosure is applied to an SBW reaction force device including a torsion bar will be described.

First, the entire SBW system including the SBW reaction device will be explained. FIG. 35 is a diagram showing an example of the configuration of the SBW system in correspondence with the general configuration of the electric power steering device shown in FIG. 1. In FIG. In addition, the same code|symbol is attached|subjected to the same structure as the structure demonstrated in the above-mentioned Embodiment 1, 2, and detailed description is abbreviate|omitted.

The SBW system does not have an intermediate shaft that is mechanically connected to the column shaft 2 at the universal joint 4a in FIG. 1, and the operation of the handle 1 is transmitted to the steering mechanism consisting of the steering wheels 8L, 8R, etc. by electric signals. It is a system. As shown in FIG. 35, the SBW system includes a reaction force device 60 and a drive device 70, and a control unit (ECU) 50 controls both devices. The reaction force device 60 detects the steering angle θh using the steering angle sensor 14, and at the same time transmits the motion state of the vehicle transmitted from the steered wheels 8L and 8R to the driver as a reaction torque. The reaction torque is generated by the reaction motor 61. Note that some SBW systems do not have a torsion bar in the reaction force device, but the SBW system to which the present disclosure is applied is a type that has a torsion bar, and the torque sensor 10 detects the steering torque Ts. do. Further, the angle sensor 74 detects the motor angle θm of the reaction force motor 61. The drive device 70 drives a drive motor 71 in accordance with the driver's steering of the steering wheel 1, and applies the driving force to the pinion rack mechanism 5 through a gear 72, and then through tie rods 6a and 6b. Turn the direction wheels 8L and 8R. An angle sensor 73 is arranged near the pinion rack mechanism 5, and detects the turning angle θt of the steered wheels 8L, 8R. In order to cooperatively control the reaction force device 60 and the drive device 70, the ECU 50 uses information such as the steering angle θh and turning angle θt outputted from both devices, as well as the vehicle speed Vs from the vehicle speed sensor 12, to A voltage control command value Vref1 for driving and controlling the reaction motor 61 and a voltage control command value Vref2 for driving and controlling the driving motor 71 are generated.

A configuration of a third embodiment in which the present disclosure is applied to such an SBW system will be described.

FIG. 36 is a block diagram showing the configuration of the third embodiment. Embodiment 3 controls the torsion angle Δθ (hereinafter referred to as "torsion angle control") and controls the steering angle θt (hereinafter referred to as "steering angle control"), and controls the reaction force device to adjust the torsion angle. control, and the drive device is controlled by steering angle control. Note that the drive device may be controlled using other control methods.

In the torsion angle control, the torsion angle Δθ follows the target torsion angle Δθref calculated via the target steering torque generation unit 202 and the conversion unit 500 using the steering angle θh etc. using the same configuration and operation as in the second embodiment. Perform such control. The motor angle θm is detected by the angle sensor 74, and the motor angular velocity ωm is calculated by differentiating the motor angle θm by the angular velocity calculation unit 951. The steering angle θt is detected by an angle sensor 73. Further, in the first embodiment, detailed description is not given as processing within the EPS steering system/vehicle system 100, but the current control section 130 includes the subtraction section 32B, the PI control section 35, and the PWM control section shown in FIG. 36 and the inverter circuit 37, based on the motor current command value Imc output from the torsion angle control section 300a and the current value Imr of the reaction force motor 61 detected by the motor current detector 140, The reaction force motor 61 is driven to perform current control.

In the turning angle control, a target turning angle θtref is generated based on the steering angle θh in a target turning angle generation unit 910, and the target turning angle θtref is input to the turning angle control unit 920 together with the turning angle θt. The steering angle control unit 920 calculates a motor current command value Imct such that the steering angle θt becomes the target steering angle θtref. Then, based on the motor current command value Imct and the current value Imd of the drive motor 71 detected by the motor current detector 940, the current control unit 930 controls the drive motor 71 with the same configuration and operation as the current control unit 130. 71 to perform current control. Note that in the present disclosure, the motor current command value Imct calculated by the steering angle control section 920 is also output to the target steering torque generation section 202.

FIG. 37 is a diagram illustrating an example of the configuration of the target turning angle generation section. The target turning angle generation section 910 includes a restriction section 931, a rate restriction section 932, and a correction section 933.

The limiting unit 931 limits the upper and lower limits of the steering angle θh and outputs the steering angle θh1. Similar to the output limiting section 350 in the torsion angle control section 300a shown in FIG. 33, an upper limit value and a lower limit value for the steering angle θh are set in advance to apply a limit.

In order to avoid sudden changes in the steering angle, the rate limiting unit 932 sets a limit value to limit the amount of change in the steering angle θh1, and outputs the steering angle θh2. For example, if the difference from the steering angle θh1 one sample before is the amount of change, and the absolute value of the amount of change is larger than a predetermined value (limit value), the steering angle is set so that the absolute value of the amount of change becomes the limit value. The steering angle θh1 is added or subtracted and output as the steering angle θh2, and if it is less than the limit value, the steering angle θh1 is output as is as the steering angle θh2. Note that instead of setting a limit value for the absolute value of the amount of change, it is also possible to set an upper limit value and a lower limit value for the amount of change. A limit may be placed on the rate.

The correction unit 933 corrects the steering angle θh2 and outputs the target turning angle θtref. For example, the target turning angle θtref is determined from the steering angle θh2 using a map that defines the characteristics of the target turning angle θtref with respect to the magnitude |θh2| of the steering angle θh2. Alternatively, the target turning angle θtref may be obtained by simply multiplying the steering angle θh2 by a predetermined gain.

FIG. 38 is a diagram illustrating a configuration example of a steering angle control section. The steering angle control unit 920 has the same configuration as the configuration example of the torsion angle control unit 300a shown in FIG. 33 except that the stabilization compensation unit 340 and the addition unit 362 are removed. The target steering angle θtref and the steering angle θt are input instead of the angle Δθ, and the steering angle feedback (FB) compensation unit 921, the steering angular velocity calculation unit 922, the speed control unit 923, the output limiting unit 926, and the subtraction unit 927 However, the torsion angle FB compensation section 310, torsion angular velocity calculation section 320, speed control section 330, output limiting section 350, and subtraction section 361 have the same configuration and perform the same operations.

In such a configuration, an example of the operation of the third embodiment will be described with reference to the flowchart of FIG. 39. FIG. 39 is a flowchart showing an example of the operation of the third embodiment.

When the operation starts, the angle sensor 73 detects the steering angle θt, the angle sensor 74 detects the motor angle θm (step S110), the steering angle θt is sent to the steering angle control unit 920, and the motor angle θm is sent to the angular velocity. Each is input to the calculation unit 951.

The angular velocity calculation unit 951 calculates the motor angular velocity ωm by differentiating the motor angle θm, and outputs the calculated motor angular velocity ωm to the torsion angle control unit 300a (step S120).

Thereafter, the target steering torque generation unit 202 executes operations similar to steps S10 to S40 shown in FIG. 7, drives the reaction force motor 61, and performs current control (steps S130 to S160).

On the other hand, in the steering angle control, the target steering angle generation unit 910 inputs the steering angle θh, and the steering angle θh is input to the restriction unit 931. The limiting unit 931 limits the upper and lower limits of the steering angle θh based on preset upper and lower limits (step S170), and outputs it to the rate limiting unit 932 as the steering angle θh1. The rate limiting unit 932 limits the amount of change in the steering angle θh1 using a preset limit value (step S180), and outputs it to the correcting unit 933 as a steering angle θh2. The correction unit 933 corrects the steering angle θh2 to obtain a target turning angle θtref (step S190), and outputs it to the turning angle control unit 920.

The steering angle control unit 920 that has input the steering angle θt and the target steering angle θtref calculates the deviation Δθt0 by subtracting the steering angle θt from the target steering angle θtref in the subtraction unit 927 (step S200 ). The deviation Δθt0 is input to the turning angle FB compensator 921, and the turning angle FB compensator 921 multiplies the deviation Δθt0 by a compensation value to compensate for the deviation Δθt0 (step S210), and converts the target turning angular velocity ωtref into a speed. It is output to the control section 923. The steering angular velocity calculation unit 922 inputs the steering angle θt, calculates the steering angular velocity ωtt by differential calculation with respect to the steering angle θt (step S220), and outputs it to the speed control unit 923. Speed control section 923 calculates motor current command value Imcta by IP control similarly to speed control section 330 (step S230), and outputs it to output limiting section 926. The output limiter 926 limits the upper and lower limits of the motor current command value Imcta using preset upper and lower limits (step S240), and outputs it as the motor current command value Imct (step S250).

The motor current command value Imct is input to the current control unit 930, and the current control unit 930 controls the drive motor 71 based on the motor current command value Imct and the current value Imd of the drive motor 71 detected by the motor current detector 940. 71 to perform current control (step S260).

Note that the order of data input, calculation, etc. in FIG. 39 can be changed as appropriate. Also, like the speed control section 330 in the torsion angle control section 300a, the speed control section 923 in the steering angle control section 920 performs PI control, P control, PID control, PI-D control, not IP control. control, etc., if it is possible to use any one of P, I, and D controls, and furthermore, follow-up control in the steering angle control section 920 and the torsion angle control section 300a is generally used. It is also possible to use a control structure that has the same structure. The steering angle control unit 920 can be used in a vehicle device as long as it has a control configuration in which the actual angle (here, the steering angle θt) follows the target angle (here, the target steering angle θtref). The present invention is not limited to the control configuration, and for example, a control configuration used in industrial positioning devices, industrial robots, etc. may be applied.

In the third embodiment, as shown in FIG. 35, one ECU 50 controls the reaction force device 60 and the drive device 70, but an ECU for the reaction force device 60 and an ECU for the drive device 70 are provided respectively. It's okay. In this case, the ECUs will transmit and receive data through communication. Furthermore, although the SBW system shown in FIG. 35 does not have a mechanical connection between the reaction device 60 and the drive device 70, if an abnormality occurs in the system, the column shaft 2 and the steering mechanism can be connected to each other using a clutch, etc. The present disclosure is also applicable to SBW systems that include a mechanical torque transmission mechanism that is mechanically coupled to the SBW system. In such an SBW system, when the system is normal, the clutch is turned off to allow mechanical torque transmission to be released, and when the system is abnormal, the clutch is turned on to enable mechanical torque transmission.

The torsion angle control units 300 and 300a in the first to third embodiments described above directly calculate the motor current command value Imc and the assist current command value Iac, but before calculating them, first the motor to which the output is desired is After calculating the torque (target torque), the motor current command value and the assist current command value may be calculated. In this case, to obtain the motor current command value and the assist current command value from the motor torque, a commonly used relationship between motor current and motor torque is used.

FIG. 40 is a block diagram illustrating a configuration example of a low μ road torque correction value calculating section according to the third embodiment. In the first and second embodiments described above, the self-aligning torque T _SAT estimated by the SAT estimation unit 343 (see FIG. 3) is detected by the yaw rate sensor 15 (see FIG. 1) as a physical quantity generated by tire slip. Although an example using the actual yaw rate γ or the actual lateral acceleration detected by the lateral acceleration sensor 16 (see FIG. 1) has been described, in this embodiment, as shown in FIG. 40, as a physical quantity generated by tire slip, A configuration using the motor current command value Imct calculated by the steering angle control section 920 (see FIG. 36) will be described.

As shown in FIG. 40, the low μ road torque correction value calculation unit 280d of the third embodiment includes a proportional coefficient multiplication unit 281d, a subtraction unit 282d, a torque adjustment coefficient value map unit 283d, an absolute value calculation unit 284d, including.

The motor current command value Imct is input to the absolute value calculation section 284d. The absolute value calculation unit 284d calculates the absolute value |Imct| of the input motor current command value Imct. The proportional coefficient multiplier 281d outputs a value k'' (|Imct|) obtained by multiplying the absolute value |Imct| of the input motor current command value by a predetermined proportional coefficient k'' to the subtracter 282d. The value of the proportional coefficient k'' is set to a value such that the torque signal Tref_a0 and the output value k'' (|Imct|) of the proportional coefficient multiplier 281d substantially match under normal running conditions.

The subtraction unit 282d outputs a value Tref_a0−k” (|Imct|) obtained by subtracting the output value k” (|Imct|) of the proportional coefficient multiplication unit 281d from the torque signal Tref_a0 to the torque adjustment coefficient value mapping unit 283d.

The torque adjustment coefficient value map section 283d holds a torque adjustment coefficient value map that indicates the relationship between the output value Tref_a0-k'' (|Imct|) of the subtraction section 282d and the torque adjustment coefficient value G. The characteristics of this torque adjustment coefficient value map are similar to the torque adjustment coefficient value map held by the torque adjustment coefficient value map section 283 of the first embodiment shown in FIG. This can be handled by replacing _SAT |) with the output value Tref_a0-k'' (|Imct|) of the subtraction unit 282d.

The torque adjustment coefficient value map section 283d derives and outputs the torque adjustment coefficient value G corresponding to the output value Tref_a0-k'' (|Imct|) of the subtraction section 282d using the torque adjustment coefficient value map described above. Note that the torque adjustment coefficient value G may be calculated using a mathematical formula that indicates the relationship between the output value Tref_a0-k'' (|Imct|) of the subtraction unit 282d and the torque adjustment coefficient value G.

In the configuration of Embodiment 3 shown in FIG. 40, similarly to the configurations according to Embodiments 1 and 2 described above, in a state where the grip force of the tire is lost, the torque signal Tref_a is changed to the normal driving state (as shown in FIG. 15). (solid line) (broken line in FIG. 15). This makes the steering feel lighter than in normal driving conditions, allowing the driver to recognize that the tires have lost grip, and allowing him to perform appropriate emergency avoidance maneuvers.

(Modified example)
FIG. 41 is a block diagram showing a configuration example of a low μ road torque correction value calculating section according to a modification of the third embodiment. Note that the same components as those in the third embodiment described above are given the same reference numerals and redundant explanations will be omitted.

As shown in FIG. 41, the low μ road torque correction value calculation unit 280e receives the torque signal Tref_a0 output from the basic map unit 210 and the motor current calculated by the steering angle control unit 920 (see FIG. 39). In addition to the command value Imct, the vehicle speed Vs is input.

As shown in FIG. 41, the low μ road torque correction value calculation section 280e of the modification of the third embodiment includes a proportional coefficient multiplication section 281e, a subtraction section 282e, a torque adjustment subtraction value mapping section 283e, and an absolute value calculation section. 284e.

The motor current command value Imct is input to the absolute value calculation unit 284e. The absolute value calculation unit 284e calculates the absolute value |Imct| of the input motor current command value Imct. The proportional coefficient multiplier 281e outputs a value k'' (|Imct|) obtained by multiplying the absolute value |Imct| of the input motor current command value by a predetermined proportional coefficient k'' to the subtracter 282e. The value of the proportional coefficient k'' is set to a value such that the torque signal Tref_a0 and the output value k'' (|Imct|) of the proportional coefficient multiplier 281e substantially match under normal running conditions.

The subtraction unit 282e outputs a value Tref_a0−k” (|Imct|) obtained by subtracting the output value k” (|Imct|) of the proportional coefficient multiplication unit 281e from the torque signal Tref_a0 to the torque adjustment subtraction value mapping unit 283e.

The torque adjustment subtraction value map section 283e holds a torque adjustment subtraction value map showing the relationship between the output value Tref_a0-k'' (|Imct|) of the subtraction section 282e, the torque adjustment subtraction value S, and the vehicle speed Vs. Implementation The characteristics of the torque adjustment subtraction value map according to the modification of the third embodiment are similar to the torque adjustment subtraction value map held by the torque adjustment subtraction value map section 283a of the modification 1 of the first embodiment shown in FIG. This can be handled by replacing the output value Tref_a0-k (|T _SAT |) of the subtraction unit 282a with the output value Tref_a0-k'' (|Imct|) of the subtraction unit 282e.

The torque adjustment subtraction value map section 283e derives and outputs the torque adjustment subtraction value S according to the output value Tref_a0-k'' (|Imct|) of the subtraction section 282e using the above-described torque adjustment subtraction value map. Note that the torque adjustment subtraction value S may be calculated using a mathematical formula showing the relationship between the output value Tref_a0-k'' (|Imct|) of the subtraction unit 282e, the torque adjustment subtraction value S, and the vehicle speed Vs. .

Similarly to the configuration according to the first embodiment described above, in the configuration of the modification of the third embodiment shown in FIG. 41, when the tire grip force is lost, the torque signal Tref_a is set to (solid line) (broken line in FIG. 15). This makes the steering feel lighter than in normal driving conditions, allowing the driver to recognize that the tires have lost grip, and allowing him to perform appropriate emergency avoidance maneuvers.

In addition, in the above-mentioned Embodiment 3 and its modifications, a configuration is exemplified in which the motor current command value Imct calculated by the steering angle control unit 920 (see FIG. 39) is used as the physical quantity generated by tire slip. Also in this embodiment, as in the second and third variations of the first embodiment, the actual yaw rate γ detected by the yaw rate sensor 15 (see FIG. 1) is used as the physical quantity generated by tire slip. is also possible. Also, in this embodiment, for example, the actual lateral acceleration detected by the lateral acceleration sensor 16 (see FIG. 1) may be used as the physical quantity caused by tire slip, similar to the first and second embodiments described above. effect can be obtained.

Furthermore, in the first embodiment described above, the motor current command value Iref generated by the torsion angle control section 300 (see FIG. 5) may be used as the physical quantity generated by tire slip, or In the second embodiment, the motor current command value Imc calculated by the twist angle control section 300a (see FIG. 25) may be used as the physical quantity generated by tire slip.

Note that the diagrams used above are conceptual diagrams for qualitatively explaining the present disclosure, and are not limited thereto. Further, although the above-described embodiment is an example of a preferred implementation of the present disclosure, the present disclosure is not limited thereto, and various modifications can be made without departing from the gist of the present disclosure. Furthermore, the mechanism is not limited to a torsion bar as long as it has an arbitrary spring constant between the handle and the motor or reaction force motor.

1 Handle 2 Column shaft 2A Torsion bar 3 Reduction mechanism 4a, 4b Universal joint 5 Pinion rack mechanism 6a, 6b Tie rod 7a, 7b Hub unit 8L, 8R Steering wheel 10 Torque sensor 11 Ignition key 12 Vehicle speed sensor 13 Battery 14 Steering angle sensor 15 Yaw rate sensor 16 Lateral acceleration sensor 20 Motor 30,50 Control unit (ECU)
60 Reaction force device 61 Reaction force motor 70 Drive device 71 Drive motor 72 Gear 73 Angle sensor 100 EPS steering system/vehicle system 130 Current control unit 140 Motor current detector 200, 200a, 200b, 200c, 201, 201a, 202 Target steering torque generation section 210 Basic map section 211 Multiplication section 212 Subtraction section 213 Sign extraction section 214 Multiplication section 220 Differentiation section 230 Damper gain map section 240 Hysteresis correction section 250 SAT information correction section 251 SAT calculation section 251A Conversion section 251B Angular velocity calculation section 251C Angular acceleration calculation section 251D, 251E, 251F Block 251H, 251I, 251J Adder 252 Filter section 253 Steering torque sensitive gain section 254 Vehicle speed sensitive gain section 255 Steering angle sensitive gain section 256 Limiting section 260 Multiplying section 261, 262, 263 Addition Parts 280, 280a, 280b, 280c, 280d, 280e Low μ road torque correction value calculation part 281, 281a, 281b, 281c, 281d, 281e Proportional coefficient multiplication part 282, 282a, 282b, 282c, 282d, 282e Subtraction part 283, 283b, 283d Torque adjustment coefficient value map section 283a, 283c, 283e Torque adjustment subtraction value map section 284, 284a, 284b, 284c, 284d, 284e Absolute value calculation section 300, 300a Torsion angle control section 310 Torsion angle feedback (FB) compensation Section 320 Torsion angular velocity calculation section 330 Speed control section 331 Integration section 332 Proportional section 333, 334 Subtraction section 340 Stabilization compensation section 350 Output limiting section 360 Rudder angle disturbance compensation section 361 Subtraction section 362, 363 Addition section 370 Reduction ratio section 400 Steering Direction determining unit 500 Conversion unit 910 Target turning angle generation unit 920 Turning angle control unit 921 Turning angle feedback (FB) compensation unit 922 Turning angular velocity calculation unit 923 Speed control unit 926 Output limiting unit 927 Subtraction unit 930 Current control unit 931 Limiting section 933 Correction section 932 Rate limiting section 940 Motor current detector 1001 CPU
1005 Interface 1006 A/D converter 1007 PWM controller 1100 Control computer (MCU)

Claims (9)

A vehicle steering device that assists and controls a vehicle's steering system by driving and controlling a motor that assists steering force, the vehicle steering device comprising:
comprising a target steering torque generation unit that generates a target steering torque for the motor;
The target steering torque generation unit includes:
The target steering torque is determined by multiplying the torque signal by a torque adjustment coefficient value corresponding to the difference between a torque signal corresponding to the steering angle and vehicle speed and a value obtained by multiplying the physical quantity generated by tire slip by a predetermined proportional coefficient. Generate vehicle steering device. The target steering torque generation unit includes:
The vehicle steering device according to claim 1 , wherein the larger the difference value is, the smaller the torque adjustment coefficient value is. The vehicle steering device according to claim 1 or 2, wherein the torque adjustment coefficient value is a positive value of 1 or less. A vehicle steering device that assists and controls a vehicle steering system by driving and controlling a motor that assists steering force, the vehicle steering device comprising:
comprising a target steering torque generation unit that generates a target steering torque for the motor;
The target steering torque generation unit includes:
A target steering torque is determined by subtracting from the torque signal a torque adjustment subtraction value corresponding to the difference between a torque signal corresponding to the steering angle and vehicle speed and a value obtained by multiplying a physical quantity generated by tire slip by a predetermined proportionality coefficient. Generate vehicle steering device. The target steering torque generation unit includes:
The vehicle steering device according to claim 4 , wherein the larger the difference value, the larger the torque adjustment subtraction value. The vehicle steering device according to claim 4 or 5 , wherein the torque adjustment subtraction value is smaller than the torque signal. The vehicle steering device according to any one of claims 1 to 6 , wherein the physical quantity is self-aligning torque. The vehicle steering device according to any one of claims 1 to 6 , wherein the physical quantity is a yaw rate. The vehicle steering device according to any one of claims 1 to 6 , wherein the physical quantity is a current command value for the motor.

Images